In the manufacture of semiconductor devices, ion implantation is used to dope semiconductors with impurities. Ion implantation systems are often utilized to dope a workpiece, such as a semiconductor wafer, with ions from an ion beam, in order to either produce n- or p-type material doping, or to form passivation layers during fabrication of an integrated circuit. Such beam treatment is often used to selectively implant the wafers with impurities of a specified dopant material, at a predetermined energy level, and in controlled concentration, to produce a semiconductor material during fabrication of an integrated circuit. When used for doping semiconductor wafers, the ion implantation system injects a selected ion species into the workpiece to produce the desired extrinsic material. Implanting ions generated from source materials such as antimony, arsenic, or phosphorus, for example, results in an “n-type” extrinsic material wafer, whereas a “p-type” extrinsic material wafer often results from ions generated with source materials such as boron, gallium, or indium.
A typical ion implanter includes an ion source, an ion extraction device, a mass analysis device, a beam transport device and a wafer processing device. The ion source generates ions of desired atomic or molecular dopant species. These ions are extracted from the source by an extraction system, typically a set of electrodes, which energize and direct the flow of ions from the source, forming an ion beam. Desired ions are separated from the ion beam in a mass analysis device, typically a magnetic dipole performing mass dispersion or separation of the extracted ion beam. The beam transport device, typically a vacuum system containing a series of focusing devices, transports the ion beam to the wafer processing device while maintaining desired properties of the ion beam. Finally, semiconductor wafers are transferred in to and out of the wafer processing device via a wafer handling system, which may include one or more robotic arms, for placing a wafer to be treated in front of the ion beam and removing treated wafers from the ion implanter.
Batch-type ion implanters are well known, which typically include a spinning disk support for moving multiple silicon wafers through the ion beam. The ion beam impacts the wafer surface as the support rotates the wafers through the ion beam. Serial-type ion implanters are also known, which treat one wafer at a time. The wafers are supported in a cassette and are withdrawn one at time and placed onto a wafer support. The wafer is then oriented in an implantation orientation so that the ion beam strikes the single wafer. These serial implanters use beam shaping electronics to deflect the beam from its initial trajectory and often are used in conjunction with coordinated wafer support movements to selectively dope or treat the entire wafer surface. As wafers are processes through an ion implantation system they are transferred between specialized processing chambers and wafer input/output stations. Robots are routinely used to transfer wafers in to and out of the processing chamber.